Pass WAI-ARIA states into dropdown

[jmacqueen]

This will pass the following WAI-ARIA relationship and widget attributes through to basic-dropdown in an attempt to complete #293

I have a thing about alphabetizing long property lists to help out when exploring or debugging, I hope that doesn't cause too much trouble. Other than alphabetizing, these are the only actual additions to the templates.

power-select attribute	WAI-ARIA attribute in DOM	Note
ariaDescribedBy	aria-describedby
ariaInvalid	aria-invalid
ariaLabel	aria-label	This one still needs to be added to basic-dropdown, but inclusion here ahead of time doesn't break anything
ariaLabelledBy	aria-labelledby
required	aria-required

I didn't include tests because I'm a bad person. And I didn't want to take the time on the off-chance these changes don't go in 😄

[cibernox]

I agree that I not longer need this polyfill, but it concerns me that this test is not failing in 1.13 in travis.

Nothing for your to change, just a note to myself.

[cibernox]

I don't mind the alphabetically order. I started grouping properties "conceptually", but clearly there was a moment where that stopped scaling 😅 . This is better now.

This does need tests tho (and probably some work in ember-basic-dropdown itself).

[cibernox]

Tests in ember-basic-dropdown and ember-power-select overlap a bit, but I try to have tests in EPS for behaviours that are anyway tested in EBD because sometimes they depend of EPS forwarding the proper properties, so in this case the duplication has a purpose.

[jmacqueen]

I've ended up duplicating in similar ways (and for similar reasons) in the widget set I'm making at work. It's helped to catch refactoring problems when I thought I was safely changing something isolated in one component...and it ends up I was wrong!

Especially considering the case of integration tests, in my opinion, it's well worth having all the relevant tests for the EPS interface in the EPS repo...even if it means tests aren't technically as DRY as they could possibly be.

[jmacqueen]

Tests added. I went ahead and put in tests for aria-label that will fail until ariaLabel is added to cibernox/ember-basic-dropdown and the updated version included. But it shouldn't break anything to go ahead and merge this as-is.

[cibernox]

@jmacqueen mmm... why travis is not running for the last commit? Also, should we update ember-basic-dropdown first?

[cibernox]

Rebase over master to get the version of EPS with support for aria-label.

[cibernox]

Thanks for all the a11y work.

This starts to look complete.